Paint comprising a liquid phase and an active powder phase

ABSTRACT

Coating composition comprising a liquid first phase comprising one or more polymer binder components having functional groups capable of cross-linking by electron pair exchange, and a second phase which is a powder material, such as sand, comprising one or more compounds capable of activating crosslinking of the binder components in the liquid phase after the second phase is exposed to the first phase. The activating compound in the second phase may include a Lewis acid or Lewis base. Method of applying a coating composition curable by cross-linking chemistry based on electron pair exchange, wherein after application of a layer of the coating composition on a substrate, a powder material comprising one or more cross-linking activating compounds is sprinkled over the wet layer. After sprinkling the powder material over the coating layer, a second coating layer is applied.

The invention relates to a coating composition comprising a liquid firstphase comprising one or more polymer binder components having functionalgroups capable of cross-linking, and a separate second phase which is adry, sprinkleable powder material comprising one or more compoundscapable of activating cross-linking of the binder components in theliquid phase after the first and second phases are exposed to eachother. The invention also pertains to a method for application of such acoating composition.

U.S. Pat. No. 5,348,763 discloses a road marking paint comprising apolymeric binder which is cured by sprinkling peroxide bearing beadsonto the wet paint. EP-A 0 389 060 discloses a powder comprisingdibenzoyl peroxide used to cure a fresh paint layer based on acrylicbinders. Peroxides are detrimental to health and the environment and forinstance may not be sprinkled with bare hands. Moreover, peroxides onlyinitiate radical polymerisation and thus are limited to specific typesof binders. Oxygen in the air can cause premature inhibition of theradical polymerisation, resulting in a tacky layer with a low degree ofcuring.

The object of the invention is to provide a coating system which allowsa balance of easy and safe application on the one hand and fast curingon the other, and which results in a durable coating layer.

The object of the invention is achieved with a coating compositioncomprising one or more polymer binders which are cross-linkable by polarreaction and at least one catalyst, the cross-linkable polymer bindersbeing comprised in a liquid phase and a separate dry sprinkleable powderphase comprising at least part of the catalyst and/or of a precursor ofthe catalyst which can form the catalyst in reaction with a co-reactivecompound in the liquid phase after the liquid phase and the powder phaseare exposed to each other. Polar reactions are non-radical reactions. Noradical formation takes place.

Polar reactions take place between nucleophiles and electrophiles andinvolve electron pair exchange.

Such cross-linking cannot be inhibited by oxygen and can be controlledmore effectively than radical copolymerisation reactions. Moreover,since cross-linking only takes place after addition of the powder phase,a very long pot life, up to about 50 hours, can be obtained.

EP-A 1 054 046 discloses a two-component coating system wherein one orboth of the components comprise a filler which can have an acceleratingeffect. Both components are aqueous. The use of a sprinkleable drypowder phase is not disclosed.

The catalyst in the powder phase can for instance include at least oneLewis acid or Lewis base. A Lewis acid is defined as a compound capableof accepting an electron pair donated by a Lewis base. Lewis acidsinclude, but are not limited to, Brönsted acids (which are, in turn,defined as proton donors), whereas Lewis bases include, among others,Brönsted bases (defined as proton acceptors). Suitable metal complexesor metal salts can also act as Lewis acids or bases, respectively.

The liquid first phase can for instance be a two-component ormulti-component composition. Two-component coating compositions arecoating compositions comprising two or more reactive compounds which arepacked and stored separately to prevent premature cross-linking. Justbefore or during application of the coating, the components are mixed.

Such a two-component system can for instance be based on isocyanatecross-linking chemistry, using polyisocyanates to cross-link compoundscomprising functional groups with active hydrogens, such as polythiolsor polyols.

Suitable polyisocyanates are for instance aliphatic, cycloaliphatic, andaromatic isocyanates, with an average isocyanate functionality of forinstance about 2.5 to about 5. The polyisocyanate can for instance be abiuret, urethane, uretdione or isocyanurate derivative. Examples ofsuitable aliphatic diisocyanates are trimethylene diisocyanate,tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylenediisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate,2,3-butylene diisocyanate, 1,3-butylene diisocyanate, ethylidenediisocyanate, butylidene diisocyanate, 4,4′-bis(isocyanate hexyl)methane, bis(2-isocyanate-ethyl) fumarate, 2,6- diisocyanate methylcaproate, 2,2,4-(2,2,4)-trimethyl hexamethylene diisocyanate, and dimeracid diisocyanates. Suitable cycloaliphatic diisocyanates are forinstance isophorone dilsocyanate, 1,3-cyclopentane diisocyanate,1,4-cyclopentane diisocyanate, 1,2 diisocyanate, or methylcyclohexylenediisocyanate. Suitable aromatic diisocyanates are for instancem-phenylene diisocyanate, p-phenylene diisocyanate, and 4,4′-diphenyldiisocyanate. Also 4,4′-diphenylene methane diisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylene diisocyanate, 4,4′-toluidene diisocyanate or1,4 xylylene diisocyanate can be used. Aromatic diisocyanates are forinstance dianisidine diisocyanate, 4,4′-diphenylether diisocyanate orchlorodiphenylene diisocyanate. Suitable triisiocyanates are forinstance triphenyl methane-4,4′-4″-triisocyanate, 1,3,5-triisocyanatebenzene or 2,4,6-triisocyanate toluene. Tetraisocyanates, such as4,4′-diphenyl dimethylmethane 2,2′,5,5′-tetraisocyanate, can also beused. Other suitable isocyanate cross-linking agents are for examplepolymerised isocyanates, e.g. tolylene diisocyanate dimers, trimers andthe like, or polyisocyanates which are derived from a polyol, includingfor example glycols such as ethylene glycol or propylene glycol;glycerol, trimethylol propane, hexane triols, pentaerythritol ormonoethers, such as diethylene glycol or tripropylene glycol. Alsosuitable are polyether polyols or polyester polyols, e.g.isocyanate-terminated prepolymers, which are the reaction product ofpolyethers with an excess of polyisocyanates.

The polyol used in the coating composition can be a polyester polyol, apolyacrylate polyol, a polyester/polyacrylate hybrid polyol, a polyetherpolyol, a polyurethane polyol, or any other suitable hydroxy-functionalpolymer or mixture of polymers. Polyacrylate polyols and polyesterpolyols are preferred.

The polyols have on average two or more hydroxy groups per molecule,preferably three or more. Preferably, the polyol or mixture of polyolshas a hydroxy value from 30 to 300 mg KOH/gram polyol, more preferablybetween 50 and 200 mg KOH/gram polyol. Most preferably, the hydroxyvalue is between 15 and 200 mg KOH/gram polyol.

Suitable polyols may for instance have an acid number below 75 mgKOH/gram polyol, preferably between 5 and 50 mg KOH/g.

A hydroxy-functional polyester can be prepared by the polyesterificationof polycarboxylic acids, their anhydrides or dialkylesters withpolyalcohols. In order to achieve hydroxy functionality in the resultingpolyester, an excess of the hydroxy component should be used. Dependingon the conversion of the functional groups, polyesters with hydroxy aswell as carboxylic acid-functional groups can be prepared.

Hydroxy-functional monomers or oligomers suitable for use in polyestersynthesis include dihydric alcohols, or diols, trihydric alcohols, ortriols, or higher alcohols. Suitable diols include (cyclo)alkane diols,for example, ethane diol, 1,2- and 1,3-propane diol, 1,2-, 1,3- and1,4-butane diol, 1,5-pentane diol, 1,6-hexane diol, neopentyl glycol,1,4-cyclohexane dimethanol, 1,2- and 1,4-cyclohexane diol,2-ethyl-2-butylpropanediol. Glycol ethers, such as diethylene glycol,triethylene glycol, tetraethylene glycol, dipropylene glycol,tripropylene glycol, polyethylene glycol, polypropylene glycol orpolybutylene glycol, can also be used. Reaction products of theaforementioned diols with 6-caprolactone can likewise be used as diols.Triols or higher alcohols suitable for polyester synthesis are forexample glycerol, trimethylol propane, pentaerythritol,dipentaerythritol, and sorbitol, and reaction products of these alcoholswith ethylene oxide and/or propylene oxide or with ε-caprolactone.Monoalcohols such as ethanol, 1- and 2-propanol, etc., can be used aschain stoppers.

Acid-functional compounds suitable for polyester synthesis includedicarboxylic acids and/or anhydrides thereof such as phthalic acid,phthalic anhydride, isophthalic acid, tetrahydrophthalic acid,tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalicanhydride, maleic anhydride, fumaric acid, succinic acid, succinicanhydride, adipic acid, dodecanedioic acid, and hydrogenated dimericfatty acids.

For obtaining excellent hydrolytic stability as well as excellentmechanical properties acids such as isophthalic acid, terephthalic acid,1,4-cyclohexane dicarboxylic acid, and hexahydrophthalic anhydride canbe selected.

Higher-functional carboxylic acids or anhydrides thereof, for exampletrimellitic acid and trimellitic anhydride, can also be used.Optionally, monocarboxylic acids may be used in the polyester synthesis,for example benzoic acid, cyclohexane-carboxylic acid, 2-ethylhexanoicacid, hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid,natural and synthetic fatty acids.

Polyacrylic polyols can be made by addition polymerisation ofethylenically unsaturated compounds. Suitable unsaturated compoundsinclude olefinically unsaturated esters comprising at least one maleicacid di(cyclo)alkyl ester having 1 to 12, preferably 1 to 8, and morepreferably 1 to 4 carbon atoms in the (cyclo)alkyl radical; maleic aciddimethyl ester, maleic acid diethyl ester, maleic acid di-n-butyl ester,maleic acid di-2-ethylhexyl ester, maleic acid di-n-decyl ester, maleicacid di-n-dodecyl ester, and maleic acid dicyclohexyl ester are suitableexamples. Further suitable unsaturated compounds are (cyclo)alkyl esterof acrylic and/or methacrylic acid having 1 to 18, preferably 1 to 12,and more preferably 1 to 9 carbon atoms in the (cyclo)alkyl radical, forexample methyl (meth)acrylate, ethyl (meth)acrylate, propyl(meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate,isobutyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate,3,3,5-tri-methylcyclohexyl (meth)acrylate, stearyl (meth)acrylate,lauryl(meth)acrylate, and benzyl (meth)acrylate. Aromatic olefinicallyunsaturated monomers, such as styrene, (α)-methylstyrene, and vinyltoluene, can also be used.

Further examples of suitable unsaturated monomers are the hydroxyalkylesters of acrylic and/or methacrylic acid having 2 to 6 carbon atoms inthe hydroxyalkyl radical, and/or reaction products thereof withε-caprolactone, as well as the addition products of acrylic and/ormethacrylic acid and monoepoxy compounds, hydroxyethyl acrylate,hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropylmethacrylate, hydroxybutyl acrylate and/or hydroxybutyl methacrylate.The reaction products of (meth)acrylic acid with monoepoxy compounds,which can also turn into OH groups, are also suitable. Examples ofsuitable monoepoxides are Cardura E10® (Shell), 2-ethylhexylglycidylether, and glycidol (1,2-epoxy-3-propanol).

Ethylenically unsaturated carboxylic acids are another class of suitableunsaturated monomers. These include (meth)acrylic acid, maleic acid,fumaric acid, and maleic and/or fumaric acid semi-esters having 1 to 18carbon atoms in the alcohol radical.

Further ethylenically unsaturated compounds are, for example, β-olefinssuch as 1-octene or 1-decene; vinyl esters such as vinyl acetate, vinylpropionate, vinyl butyrate, VeoVa® 9 and VeoVa® 10 (both available fromShell), and other vinyl compounds such as N-vinyl pyrrolidone, N-vinylcaprolactam, and N-vinyl carbazole.

Polyester/polyacrylate hybrid binders can be prepared by preparing apolyester oligomer using ethylenically unsaturated acids, unsaturatedalcohols, unsaturated fatty acids or derivatives thereof such asanhydrides or esters, in particular conjugated unsaturated fatty acids.Unsaturation can also be provided by an unsaturated monoisocyanate, forexample dimethyl-m-isopropenyl benzyl isocyanate, after the polymerformation. It is also possible to prepare a carboxylic acidgroups-containing polyester, followed by reaction with an oxirangroups-containing monomer such as allyl glycidyl ether or glycidylmethacrylate. Examples of unsaturated alcohols are glycerol monoallylether, trimethylol propane monoallyl ether, butene diol and/ofdimethylol propionic acid monoallyl ether. Examples of unsaturated acidsinclude maleic acid, muconic acid, crotonic acid, citraconic acid, anditaconic acid. Preference is given to a partially unsaturatedhydroxy-functional polyester containing 0.05 to 0.5 ethylenicallyunsaturated group per molecule.

The polyester/polyacrylate hybrid resin is obtained by the additionpolymerisation of radically polymerisable unsaturated monomers in thepresence of the partially unsaturated hydroxy-functional polyesterdescribed hereinbefore. In this process, the addition polymer is linkedto the polyester resin by means of grafting onto the unsaturated groupsin the polyester. By the term “grafting” is meant an additionpolymerisation reaction to a degree of more than 0% (to a maximum of100%) of radically polymerisable monomers on the unsaturated bonds inthe polyester resin. Both the polyester and the acrylic portions of thehybrid composition can comprise sulphonate and/or carboxylate groups andpolyalkyleneoxide groups. Alternatively, all the sulphonate and/orcarboxylate groups and polyalkylenoxide groups can be present in thepolyester or the acrylic part of the hybrid composition.

Alternatively, or additionally, the composition can comprise one or morefurther types of polyols such as polyurethane polyols, polyether polyolsor hybrids thereof.

Examples of polythiols suitable for cross-linking by isocyanates are forinstance polythiols prepared by reacting hydroxy group-containingcompounds with thiol group-containing acids, such as 3-mercaptopropionicacid, 2-mercaptopropionic acid, thio-salicylic acid, mercaptosuccinicacid, mercaptoacetic acid, or cysteine. Examples of suitable hydroxygroup-containing compounds are diols, triols, and tetraols, such as1,4-butane diol, 1,6-hexane diol, 2,2-dimethyl-1,3-propane diol,2-ethyl-2-propyl-1,3-propane diol, 1,2-, 1,3-, and 1,4-cyclohexanediols, and the corresponding cyclohexane dimethanol, 1,1,1-trimethylolpropane, 1,2,3-trimethylol propane, and pentaerythritol. Examples ofcompounds prepared according to such a method include pentaerythritoltetrakis (3-mercapto propionate), pentaerythritol tetrakis (2-mercaptoacetate), trimethylol propane tris (3-mercapto propionate), trimethylolpropane tris (2-mercapto propionate), and trimethylol propane tris(2-mercapto acetate). Good results have been obtained with trimethylolpropane tris (3-mercapto propionate) and pentaerythritol tetrakis(3-mercapto propionate).

A further example of a compound prepared according to such a methodconsists of a hyperbranched polyol core based on a starter polyol, e.g.,trimethylol propane, and dimethylol propionic acid. This polyol issubsequently esterified with 3-mercaptopropionic acid and isononanoicacid. These methods are described in European patent application EP-A 0448 224 and International patent application WO 93/17060.

Other syntheses to prepare compounds comprising at least twothiol-functional groups involve:

-   -   the reaction of an aryl or alkyl halide with NaHS to introduce a        pendent thiol group into the alkyl and aryl compounds,        respectively;    -   the reaction of a Grignard reagent with sulphur to introduce a        pendent thiol group into the structure;    -   the reaction of a polymercaptan with a polyolefin according to a        Michael addition reaction, a nucleophilic reaction, an        electrophilic reaction or a radical reaction;    -   the reaction of a polyisocyanate with a thiol-functional        alcohol, and    -   the reduction of disulphides.

The compound comprising at least one thiol-functional group and onehydroxy-functional group may for example have a structure according tothe following formula: T[(C₃H₆O)_(n)CH₂CHOHCH₂SH]₃, with T being a trialsuch as trimethylol propane or glycerol. An example of such a compoundis commercially available from Henkel under the trademark HenkelCapcure® 3/800.

Alternatively, the isocyanate reactive compound comprising at least onethiol group is a resin having as a polyester resin, polyurethane resin,polyacrylate resin, or polyether resin as its backbone. Theseisocyanate-reactive compounds may then also comprise hydroxy groups.

The isocyanate-reactive compound comprising at least one thiol group canbe a polyester prepared from (a) at least one polycarboxylic acid orreactive derivatives thereof, (b) at least one polyol, and (c) at leastone thiol-functional carboxylic acid. The polyesters preferably possessa branched structure. Branched polyesters are conventionally obtainedthrough condensation of polycarboxylic acids or reactive derivativesthereof, such as the corresponding anhydrides or lower alkyl esters,with polyalcohols, when at least one of the reactants has afunctionality of at least 3.

Examples of suitable polycarboxylic acids or reactive derivativesthereof are tetrahydrophthalic acid, tetrahydrophthalic anhydride,hexahydrophthalic acid, hexahydrophthalic anhydride, methylhexahydrophthalic acid, methyl hexa-hydrophthalic anhydride,dimethylcyclohexane dicarboxylate, 1,4-cyclohexane dicarboxylic acid,1,3-cyclohexane dicarboxylic acid, phthalic acid, phthalic anhydride,isophthalic acid, terephthalic acid, 5-tert. butyl isophthalic acid,trimellitic anhydride, maleic acid, maleic anhydride, fumaric acid,succinic acid, succinic anhydride, dodecenyl succinic anhydride,dimethyl succinate, glutaric acid, adipic acid, dimethyl adipate,azelaic acid, and mixtures thereof.

Examples of suitable polyols include trimethylol propane, trimethylolethane, glycerol, 1,2,6-hexanetriol, ethylene glycol, 1,2-propyleneglycol, 1,3-propylene glycol, 2-methylpropane-1,3-diol, neopentylglycol, 2-butyl-2-ethyl-1,3-propane dial, cyclohexane-1,4-dimethylol,the monoester of neopentyl glycol and hydroxypivalic acid, hydrogenatedBisphenol A, 1,5-pentane diol, 3-methyl-pentane diol, 1,6-hexane diol,2,2,4-trimethyl pentane-1,3-diol, dimethylol propionic acid,pentaerythritol, di-trimethylol propane, dipentaerythritol, and mixturesthereof.

Examples of suitable thiol-functional organic acids include3-mercaptopropionic acid, 2-mercaptopropionic acid, thio-salicylic acid,mercaptosuccinic acid, mercaptoacetic acid, cysteine, and mixturesthereof.

Optionally, monocarboxylic acids and monoalcohols may be used in thepreparation of the polyesters. Preferably, C₄-C₁₈ monocarboxylic acidsand C₆-C₁₈ monoalcohols are used. Examples of the C₄-C₁₈ monocarboxylicacids include pivalic acid, hexanoic acid, heptanoic acid, octanoicacid, nonanoic acid, 2-ethylhexanoic acid, isononanoic acid, decanoicacid, lauric acid, myristic acid, palmitic acid, isostearic acid,stearic acid, hydroxystearic acid, benzoic acid, 4-tert. butyl benzoicacid, and mixtures thereof. Examples of the C₆-C₁₈ monoalcohols includecyclohexanol, 2-ethylhexanol, stearyl alcohol, and 4-tart. butylcyclohexanol.

Good results can also be obtained with an aqueous thiol-functionalpolyurethane dispersion which is obtainable by first preparing anisocyanate-functional polyurethane from diols, diisocyanates, andbuilding blocks containing groups which facilitate the stabilisation ofthe resin in an aqueous dispersion, followed by reaction of theisocyanate-functional polyurethane with a polyfunctional thiol in abase-catalysed addition reaction, followed by dispersion in water.

The isocyanate-reactive compound comprising at least one thiol group canbe a thiol-functional polyacrylate. Such a polyacrylate is derived fromhydroxy-functional acrylic monomers, such as hydroxyethyl(meth)acrylate, hydroxy-propyl (meth)acrylate, hydroxybutyl(meth)acrylate, other acrylic monomers such as (meth)acrylic acid,methyl (meth)acrylate, butyl (meth)acrylate, optionally in combinationwith a vinyl derivative such as styrene, and the like, or mixturesthereof, wherein the terms (meth)acrylate and (meth)acrylic acid referto both methacrylate and acrylate, as well as methacrylic acid andacrylic acid, respectively. The thiol group is introduced by thereaction product of dimethyl-m-isopropenyl benzyl isocyanate andmercaptoethanol. Alternatively, glycidyl methacrylate is introduced intothe polymer to prepare an epoxy-functional polyacrylate. The epoxygroups are then reacted with suitable thiol-functional organic acidssuch as mentioned above. The polyacrylate is prepared by conventionalmethods, for instance by the slow addition of appropriate monomers to asolution of an appropriate polymerisation initiator, such as an azo orperoxy initiator.

Also included in the coating compositions of the invention may be di-,tri-, or higher thiol-functional diluents such as ethane dithiol orbis-beta-mercapto-ethyl sulphide. Preference is given to the use ofhigher-molecular weight thiol-functional compounds, which can beobtained by reaction of a polythiol-functional compound with apolyisocyanate.

Preferably, the isocyanate-reactive compound comprising at least onethiol group is derived from a polyester compound. Examples thereofinclude the above-mentioned reaction product of hydroxylgroup-containing compounds with thiol group-containing acids and theabove-mentioned polyester prepared from (a) at least one polycarboxylicacid or reactive derivatives thereof, (b) at least one polyol, and (c)at least one thiol-functional carboxylic acid. The most preferredthiol-functional compound is pentaerythritol tetrakis (3-mercaptopropionate).

Suitable catalysts for thiol/isocyanate cross-linking are for instanceLewis bases comprising at least one organic compound comprising an ionof a metal of Groups 3 to 13 of the Periodic Table. The organic metalcompounds comprise metal salts and/or complexes of organic compounds.The organic compounds are groups having 2 to 40 carbon atoms, optionallycomprising atoms such as O, N, and S. The metal salts may comprisecarboxylate anions. Examples thereof include propionate, butyrate,pentanoate, 2-ethyl hexanoate, naphthenate, oxalate, malonate,succinate, glutamate, and adipate. The metal complexes comprise ligandsselected from the group of beta-diketones, alkyl acetoacetates,alcoholates, and combinations thereof. Examples thereof include acetylacetone (2,4-pentanedione), 2,4-heptanedione, 6-methyl-2,4-heptadione,2,4-octanedione, propoxide, isopropoxide, and butoxide. Examples ofmetals include aluminium, titanium, zirconium, and hafnium. Examples ofmetal complexes include aluminium complexed with 2,4-pentanedione(K-KAT® XC5218 ex King Industries), aluminium triacetyl acetonate,zirconium tetraacetyl acetonate, zirconium tetrabutoxide (Tyzor® NBZ exDupont), titanium tetra-butoxide (Tyzor® TBT ex Dupont), zirconiumcomplexed with 6-methyl-2,4-heptadione, K-KAT® XC6212 ex KingIndustries, aluminium triisopropoxide, and titanium diisopropoxidebis-2,4(pentadionate) (Tyzor® AA ex DuPont). These catalysts may be usedin an amount of 0.01 to 10 wt. % on solid curable material, preferably0.1 to 5 wt. %.

Cross-linking of the reactive compounds in the paint composition canalternatively be based on Michael addition. In such a system, anunsaturated binder component, for instance an acryloyl-functionalpolymer, is reacted with a compound comprising acidic C—H groups. Theunsaturated polymer may comprise at least one electron-withdrawingfunctionality linked to a carbon atom of the unsaturated bond. In thecompound comprising two or more olefinically unsaturated groups, theunsaturated groups comprise at least one electron-withdrawing functionalgroup linked to a carbon atom of the unsaturated group. The unsaturatedbond may be a double or a triple bond. The electron-withdrawing group orgroups may comprise carbonyl, carboxyl, ester, nitryl, cyanide,acrylamide or alkoxy functionality. Optionally non-electron-withdrawinggroups may be present such as hydrogen or linear or branched alkyl,cycloalkyl, alkenyl, cyclo-alkenyl, alkynyl, cyclo-alkynyl, aryl orcombinations thereof, which may be optionally substituted with variousfunctionalities, such as hydroxy groups. The unsaturated bindercomponent can be derived from an unsaturated carboxylic acid having 2 to10, preferably 3 to 6, carbon atoms. The carboxylic acid may be mono- orpolyunsaturated and may be a monocarboxylic or polycarboxylic acid.Examples of suitable carboxylic acids are cinnamic acid, citraconic acidor its anhydride, mesaconic acid, fumaric acid, maleic acid, propargylicacid, dehydro-levulinic acid, and itaconic acid or its anhydride.Acrylic acid, methacrylic acid, maleic acid or its anhydride, arepreferred. A suitable example of a compound comprising an acrylic estergroup is trimethylol propane triacrylate. Polyesters of diethyl maleatewith diols, such as 1,5-pentane diol, 1,3-propane diol and/or2-butyl-2-ethyl propane diol, or the reaction product of anepoxy-functional compound, such as Cardura® E10 (an aliphatic epoxycompound available from Shell Chemical Company), the trimer ofisophorone diisocyanate, e.g., Vestanat® T1890 E, available from Hüls,and isobutyl monomaleate, are also suitable. Other suitable examples arethe reaction product of maleic anhydride and dipentaerythritol, or thereaction product of maleic anhydride, isophorone diisocyanate, andbutanol. Alternatively, the unsaturated binder component can be derivedfrom an unsaturated ketone, such as divinyl ketone or dibenzal acetone.Unsaturated nitriles, for example maleic acid mononitrile-monoesters ofpolyhydric alcohols, are also suitable, as are alkylidene malonic acidesters or cyanoacrylic acid esters.

Compounds comprising an acidic C—H group include for instance malonates,acetoacetates, beta-diketones, beta-keto esters, beta-keto nitriles ornitro compounds.

Suitable catalysts for Michael additions include Lewis bases having apKa of 12 or higher, such as quaternary ammonium compounds, trimethylbenzyl hydroxide ammonium, tetramethyl guanidine,diazo-bicyclo-undecene, and diazo-bicyclo-nonene.

Alternatively, use can be made of a cross-linking chemistry rathersimilar to the Michael addition but using thiol groups to provide theactive hydrogen. Such thio-Michael systems are for instance described inEP-A 0 160 824 and in WO 00/64959. The polythiols described above forisocyanate-based cross-linking are also suitable for use in thesethio-Michael systems. Similarly, the polyunsaturated compounds describedabove for cross-linking based on the classic Michael addition are alsosuitable for use in thio-Michael systems.

Suitable catalysts for thio-Michael cross-linking include the Lewisbases that are described above for Michael addition-based cross-linking.Alternatively, weaker bases can also be used, such as primary orsecondary amines, aldimines, ketimines, enamines, oxazolidines ormixtures thereof. Examples of primary amines that are suitable as acatalyst are isophorone diamine and butyl amine. A suitable secondaryamine is for instance di-octyl amine. Examples are aldimines ofisophorone diamine with n-nonyl aldehyde, n-octyl aldehyde, 2-ethylhexylaldehyde, isobutyraldehyde; monofunctional aldimines such as n-octyl- orn-nonyl amine with octyl aldehyde, nonyl aldehyde or 2-ethyl hexylaldehyde; or the condensation products of primary amino groups withacetaldehyde, propionaldehyde, isobutyraldehyde, octyl aldehyde or nonylaldehyde. Suitable ketimines are for example triamino nonane-trisethylamyl ketimine or the condensation products of primary amino groupswith for instance acetone, methylethyl ketone, methylisolbutyl ketone,methylisoamyl ketone, ethylamyl ketone, or cyclohexanone. The use ofoxazolidines, enamines or mixtures thereof as a catalyst results in amoisture-curable composition. The reaction starts slowly when thecompound comprising the oxazolidine or enamine group is added to themixture. After contact with moisture, the oxazolidine or enamine isconverted by hydrolysis into a primary or secondary amine. As a resultof the presence of the primary or secondary amines, the reaction isgradually accelerated. An example of a suitable enamine is1-pyrrolidino-1-cyclohexene. A suitable tertiary amine is dimethyl aminoethanol.

A further possible cross-linking system for a coating compositionaccording to the invention is one based on cross-linking ofepoxy-functional compounds with epoxy-reactive compounds, such asbinders having carboxylic acid groups, polyamines and/or polythiols.Suitable polyepoxies are for instance Epikote® 235, 255, 1001, 1004, or1009, all available from Shell. The polythiols listed above for theNCO-thiol curing systems are also suitable for systems based onepoxy-thiol curing. A suitable catalyst for epoxy-thiol or epoxy-aminecuring is for instance 1,4-diazabicyclo[2,2,2]octane. Suitable examplesof catalysts for epoxy-acid curing are for example tetraalkyl ammoniumiodide, tetraalkyl ammonium bromide, and chromium III 2-ethyl hexanoate.

The liquid phase may be water borne or solvent borne, but particularlyfor cases where the paint does not need to be sprayable, the compositionmay be solvent-free.

The liquid phase may further contain the usual additives, such asfillers, pigments, flow additives, rheology modifiers, defoamers, UVabsorbers, or other additives. Vitreous beads may be added, e.g. if thecomposition is used as a road marking paint.

The second phase of the coating composition according to the presentinvention is a powder material suitable for catalysing curing of theliquid phase. The powder material may for instance comprise a compoundcapable of in situ formation of a base when mixed into the liquid phase.To this end, the liquid phase may for example comprise a phosphinecompound, whereas the powder phase may comprise one or more compoundshaving an electron-deficient olefin-functional group, or the other wayaround if so desired. When the phosphine compound is exposed to theolefin compound, a basic complex is formed which in turn catalyses thecross-linking reaction. A suitable phosphine compound is for instancetriphenyl phosphine. Suitable electron-deficient olefins are forinstance acrylates, methacrylates, maleates, fumarates, andmalein-imides.

Alternatively, the powder material can comprise one or more compoundswhich are basic per se, such as the above listed amine-functionalcompounds.

The powder material may comprise a carrier material, such as a silicate,carrying the catalysing compounds. Suitable silicate carriers are forexample sand, vitreous beads, diatomaceous earth, and zeolites. Suitablenon-silicate carriers are for instance barium sulphate, chalk, organicpigments or inorganic pigments, such as titanium dioxide. The activatingcompounds can be adsorbed onto the surface of the carrier materialparticles.

If sand is used as a carrier material, the roughness of the paint layerafter curing can be increased by using a high average particle size.This can be combined with the use of finer grades of sand having asmaller average particle size to fill the intermediate space between thelarger particles and to increase the specific surface to which thecatalyst compound can attach itself. In a suitable embodiment, thepowder comprises a mixture of sand having an average particle size above200 micrometers and a fine sand having an average particle size below100 micrometers. In a more specific example of a suitable embodiment,the powder comprises more than about 60 wt. % of sand having an averageparticle size between 300-800 micrometers, 15-30 wt. % of quartz sandhaving an average particle size of 20-90 micrometers, and a fine gradequartz sand having an average particle size below 10 micrometers,preferably about 3 micrometers.

The powder material may for instance comprise up to about 8 wt. % of thecatalysing compound, although in particular cases up to about 5 wt. %,or up to about 3 wt. % may be sufficient.

Instead of using a powder carrier material, an activating compound canbe used which is itself a solid powder material. Suitable examples arezinc oxide, calcium oxide, calcium carbonate or zirconia treatedtitanium dioxide, such as Tioxide® TR92, available from Huntsman.

The invention also relates to a method of applying a coating compositioncurable by cross-linking chemistry based on electron pair exchange,wherein after application of a layer of the coating composition on asubstrate, a powder material comprising one or more cross-linkingactivating compounds is sprinkled over the wet layer. The powdermaterial can be sprinkled over the paint layer by hand. Superfluouspowder material may be swept away. If so desired, sand blasters orblowers may be used

If the thickness of the freshly applied coating layer is less than theparticle size of at least a part of the powder material, the powderparticles will protrude from the fresh paint layer. A second coatinglayer can then be applied after sprinkling the powder material over thefirst coating layer. Since the particles sprinkled over the first layerwill protrude into the layer applied second, the catalysing compoundwill also activate curing in the second layer.

The method according to the present invention is particularly suitablefor application of floor coatings having rough surfaces, such as foraccess balconies for deck access flats, road marking paints, or coatingsfor wearing course surfaces, e.g. garage floors or parking garagefloors.

The invention is further described and illustrated by the followingexamples. In the examples, all amounts are given in percentages byweight unless indicated otherwise.

EXAMPLE 1

A two-component coating composition was prepared. The first componentcomprised pentaerythritol tetrakis 3-mercaptopropionate (PET-3-MP,available form Bruno Bock), 20 wt. % titanium dioxide (Tipure® R902-38,available from Dupont), about 0.6 wt. % of a defoamer (Byk® A525), about0.1 wt. % of a surfactant (Byk® 307), and 1 wt. % triphenyl phosphine(available from Rhodia) in xylene (ratio 1:2). The second componentcomprised a polyisocyanate (Tolonate® HDT LV, available from Rhodia).

The components were stoichiometrically mixed before application. Afterapplication with a roller, a powder material was sprinkled over theapplied paint layer. The powder comprised: 6 parts of sand having anaverage particle size ranging from 0.3-0.8 mm, 2 parts of a rough gradequartz sand having an average particle size of about 50 micrometers, anda fine grade quartz sand having an average particle size of about 3micrometers. Furthermore, the powder material comprised 2 wt. % of anacrylate (Actilane® 411, available from Akcros). A substantial part ofthe particles protruded from the paint layer.

Curing was completed within 10 minutes. Excess sand was removed and asecond layer of paint was applied on top of the cured layer with aroller. Curing of the second layer occurred within 30 minutes.

EXAMPLE 2

A two-component coating composition was prepared. The first componentcomprised pentaerythritol tetrakis 3-mercaptopropionate, about 0.6 wt. %of a defoamer (Byk® A525), about 0.1 wt. % of a surfactant (Byk® 307),and 10 wt. % titanium dioxide (Tipure® R902-38). The second componentcomprised a polyisocyanate (Tolonate® HDT LV).

The components were stoichiometrically mixed before application. Afterapplication with a roller, a powder material was sprinkled over thefresh, uncured paint layer. The powder comprised: 9 parts of glass beads(050-40-216-A2, available from Solvitec) having an average particle sizeof about 40 micrometers and 1 part of a fine grade quartz sand having anaverage particle size of about 3 micrometers. Furthermore, the powdermaterial comprised 0.5 wt. % triethanolamine.

Curing was obtained within 5 minutes.

EXAMPLE 3

A two-component coating composition was prepared. The first componentcomprised pentaerythritol tetrakis 3-mercaptopropionate, 14 wt. %titanium dioxide (Tipure® R902-38, available from Dupont), about 0.6 wt.% of a defoamer (Byk® A525), about 0.1 wt. % of a surfactant (Byk® 307).The second component comprised a polyisocyanate (Tolonate® HDT LV).

The components were stoichiometrically mixed before application. Afterapplication, a powder material was sprinkled over the applied paintlayer. The powder comprised: 9 parts of sand having an average particlesize ranging from 0.3-0.8 mm and 1 part Tioxide® TR92 (commerciallyavailable from Huntsman), a zirconia-treated TiO2.

Curing was obtained within 30 minutes.

EXAMPLE 4

A two-component coating composition was prepared. The first componentcomprised pentaerythritol tetrakis 3-mercaptopropionate, about 0.6 wt. %of a defoamer (Byk® A525), 20 wt. % titanium dioxide (Tipure® R902-38,available from Dupont), and about 0.1 wt. % of a surfactant (Byk® 307).The second component comprised a polyisocyanate (Tolonate® HDT LV).

The components were stoichiometrically mixed before application. Afterapplication, a powder material was sprinkled over the applied paintlayer. The powder consisted mainly of sand having an average particlesize ranging from 0.2-0.6 mm. Furthermore, the powder material comprised0.5 wt. % zirconium butoxide.

Curing was obtained within 30 minutes.

EXAMPLE 5

A two-component coating composition was prepared. The first componentcomprised pentaerythritol tetrakis 3-mercaptopropionate, 20 wt. %titanium dioxide (Tipure® R902-38, available from Dupont), about 0.6 wt.% of a defoamer (Byk® A525), and about 0.1 wt. % of a surfactant (Byk®307). The second component comprised a polyisocyanate (Tolonate® HOTLV).

The components were stoichiometrically mixed before application. Afterapplication, CaCO₃ was sprinkled over the applied paint layer.

Curing was obtained within 60 minutes.

EXAMPLE 6

A two-component coating composition was prepared. The first componentcomprised pentaerythritol tetrakis 3-mercaptopropionate, 20 wt. %titanium dioxide (Tipure® R902-38, available from Dupont), about 0.6 wt.% of a defoamer (Byk® A525), and about 0.1 wt. % of a surfactant (Byk®307). The second component comprised a polyfunctional acrylate(Actilane® 433, available from Akcros).

The components were stoichiometrically mixed before application. Afterapplication, a powder material was sprinkled over the applied paintlayer. The powder was a sand having an average particle size rangingfrom 02-0.6 mm. Furthermore, the powder material comprised 0.5 wt. %oxazolidine (Incozol-e, available from Industrial Copolymers Limited).

Curing was obtained within 30 minutes.

EXAMPLE 7

A two-component coating composition was prepared. The first componentcomprised a polyfunctional acetoacetate (AATMP®, available from LonzaGroup), 20 wt. % titanium dioxide (Tipure® R902-38, available fromDupont), about 0.6 wt. % of a defoamer (Byk® A525), and about 0.1 wt. %of a surfactant (Byk® 307). The second component comprised apolyfunctional acrylate (Actilane® 433, available from Akcros).

The components were stoichiometrically mixed before application. Afterapplication, a powder material (sand) was sprinkled over the appliedpaint layer. The powder had an average particle size ranging from0.2-0.6 mm. Furthermore, the powder material comprised 0.5 wt %1,8-diaza-bicyclo[5.4.0]undec-7-ene.

Curing was obtained within 5 minutes.

EXAMPLE 8

A two-component coating composition was prepared. The first componentcomprised pentaerythritol tetrakis 3-mercaptopropionate, 20 wt. %titanium dioxide (Tipure® R902-38, available from Dupont), about 0.6 wt.% of a defoamer (Byk® A525), and about 0.1 wt. % of a surfactant (Byk®307). The second component comprised a polyfunctional epoxy (Epikote®154, available from Shell).

The components were stoichiometrically mixed before application. Afterapplication, a powder material (sand) was sprinkled over the appliedpaint layer. The powder had an average particle size ranging from0.2-0.6 mm. Furthermore, the powder material comprised 1 wt. %1,4-diazabicyclo-[2,2,2]octane in ethanol (ratio: 1:2).

Curing was obtained within 15 minutes.

1. Coating composition comprising one or more polymer binderscross-linkable by polar reaction and at least one catalyst, thecross-linkable polymer binders being comprised in a liquid phase,characterised in that a separate dry sprinkleable powder phase comprisesat least a part of the catalyst and/or of a precursor of the catalystwhich forms the catalyst in reaction with a co-reactive compound in theliquid phase
 2. A coating composition according to claim 1,characterised in that at least one catalyst includes a Lewis acid orLewis base.
 3. A coating composition according to claim 1, characterisedin that the liquid phase comprises a compound which is reactive with aprecursor in the powder phase to form a Lewis base or Lewis acid afterthe liquid phase is exposed to the powder phase.
 4. A coatingcomposition according to claim 1, characterised in that the liquid phaseis a two-component composition, the first component comprising one ormore polyisocyanates and the second component comprising a polythiol,polyol, polyamine or mixtures thereof.
 5. A coating compositionaccording to claim 1, characterised in that the liquid phase is atwo-component composition, the first component comprising one or morepolyepoxies and the second component comprising one or more polythiols.6. A coating composition according to claim 1, characterised in that theliquid phase is a two-component composition, the first componentcomprising a polyunsaturated binder and at least oneelectron-withdrawing group linked to a carbon atom of at least one ofthe unsaturated bonds, the second component comprising a polythioland/or a compound comprising acidic CH groups.
 7. A coating compositionaccording to claim 3, characterised in that the powder phase comprisesone or more phosphine compounds and in that the liquid phase comprisesone or more electron-deficient olefins.
 8. A coating compositionaccording to claim 1, characterised in that the powder phase comprisesone or more amines.
 9. A coating composition according to claim 1,characterised in that the catalyst in the powder phase is a solidmaterial in powder form.
 10. A coating composition according to claim 9,characterised in that the powder is zinc oxide, calcium oxide and/orcalcium carbonate.
 11. A coating composition according to claim 1,characterised in that the powder comprises a solid carrier material inpowder form having one or more of the activating compounds adsorbed toits surface.
 12. A coating composition according to claim 11,characterised in that the carrier material is sand, diatomaceous earth,zeolite, vitreous beads, barium sulphate, chalk, pigment, or mixturesthereof.
 13. A coating composition according to claim 12, characterisedin that the powder material is titanium dioxide coated with a zirconiumcompound.
 14. A coating composition according to claim 12, characterisedin that the carrier material comprises a mixture of sand having anaverage particle size above 200 micrometers and a fine sand having anaverage particle size below 100 micrometers.
 15. A coating compositionaccording to claim 14, characterised in that it comprises more thanabout 60 wt. % of sand having an average particle size between 300-800micrometers, 15-30 wt. % of quartz sand having an average particle sizeof 20-90 micrometers, and a fine grade quartz sand having an averageparticle size below 10 micrometers, preferably about 3 micrometers. 16.A coating composition according to claim 1, characterised in that thepowder phase comprises up to about 8 wt. % of the catalyst, preferablyup to about 5 wt. %, more preferably up to about 3 wt. %.
 17. Method ofapplying a coating composition comprising in a liquid phase one or morepolymer binders cross-linkable by polar reaction and in a separate drypowder phase at least one catalyst wherein after application of one ormore layers of the liquid phase on a substrate, the powder phase issprinkled over the wet liquid phase layer.
 18. Method of applying acoating composition comprising in a liquid phase one or more polymerbinders cross-linkable by polar reaction and in a separate dry powderphase at least one precursor of a catalyst which forms the catalyst inreaction with a co-reactive compound in the liquid phase wherein afterapplication of a layer of the liquid phase on a substrate, the powderphase is sprinkled over the wet liquid phase layer.
 19. Method accordingto claim 17, characterised in that the thickness of the freshly appliedlayer of liquid phase is less than the particle size of at least a partof the powder phase material, and in that after sprinkling the powderphase over the wet liquid phase layer, a second layer of the liquidphase is applied.